Alloys of titanium containing aluminum and iron



Patented Jan. 19, 1954 ALLOYS F TITANIUM CONTAINING ALUMINUM AND IRONRobert H. Dickinson and Lee S. Busch, Indianapolis, Ind., assignors, bymesne assignments,

to Mallory-Sharon Titanium Corporation, Indianapolis, Ind., acorporation of Delaware No Drawing. Application July 24, 1951, SerialNo. 238,392

2 Claims. (01. 75-177) This invention relates to titanium base alloy andmore particularly to ductile wrought alloys of titanium, aluminum andiron. 7

It is an object of the present invention to pro vide strong ductilealloys of titanium.

It is another object of the present invention to provide ductile wroughtalloys of titanium, aluminum and iron which have good resistance tooxidation and high hardness at elevated temperatures, as well as tensileproperties improved over the metal titanium alone.

A further object of the present invention is to provide ternary alloysof titanium, aluminum and iron and to which may be added the elementsilicon to form a quaternary alloy. It is, therefore, an object of thepresent invention to provide alloys of titanium, aluminum and iron towhich may be added the element silicon providing a new quaternary alloyof titanium, aluminum, iron and silicon.

Another object of the present invention is to provide strong ductilealloys of titanium, alumi-' num and iron to which the elements carbon orsilicon may be added to form additional alloys of titanium, aluminum,iron, carbon, and/or alloys of titanium, aluminum, iron, carbon andsilicon.

Another object of the present invention is to provide methods forforming ductile alloys of titanium containing predominantly aluminum andiron and to which may be added the elements silicon and/or carbon toform quaternary or quintenary alloys having as a prime base therefor theelements titanium, aluminum and iron. v

It is also within the contemplation of the invention to provide meansfor making titanium base alloys containing aluminum, iron and titaniumof improved physical properties on a practical and industrial scale atlow cost.-

It has been discovered that aluminum and iron form strong ductileternaryalloys within titanium. It has also been found that carbon may be addedto the aforesaid ternary alloy containing aluminum, titanium and ironand by such addition the properties of the alloy may be materiallyafiected. If carbon is added to the ternary alloy of titanium, aluminumand iron,

it has been found that the range of carbon introduced therein may befrom 0.25% to 0.75%

thereof. Below this range, the beneficial eifects of the carbon, it hasbeen found, decrease materially, while above this range the elongationof the alloy to which the carbon has been added is reduced appreciably.

Thus, in accordance with the results obtained Ultimate tensile strength(p. s. i.) 146,000

Proportional limit (p. s. i.) 112,000 Elongation (per cent in 2") 13.3Reduction in area (per cent) 39.7 Modulus of elasticity (p. s. i.) 18 10Electrical resistivity (ohm-cm.) v 138x10- For comparison, unalloyedtitanium had the following properties when containing the sameimpurities as the alloy above:

Ultimate tensile strength (p. s. i.) 87,000 Proportional limit (p. s.i.) 53,000 Elongation (per cent in 2") 16 Modulus of elasticity (p. s.i.) l6 10 Electrical resistivity (ohm-cm.) x10- It is to be noted, thebasic alloy of the present invention is a ternary alloy of aluminum,iron and titanium. The ternary alloy thus formed is significantlyimproved over the binary alloys of aluminum and titanium and iron andtitanium. The former binary alloy, it has been found,are difiicult tohot work. For example, when the aluminum content is greater than 2.5% insuch a binary alloy, it is very diificult to hot work. On the otherhand, alloys consisting of titanium and iron are very quench hardenableand it is diflicult to prevent cracking during forming operations.

When the alloy of titanium, iron and aluminum is provided, however,entirely unexpected results result. This is readily observable from acomparison of properties as disclosed in the alloys containing (1)titanium, aluminum and carbon; (2) titanium, iron and carbon; ascompared to (3) ternary alloy of aluminum, iron, titanium, plus theaddition of carbon:

Elongation (per cent in 2") 0 Electrical resistivity (ohm-cm.) 10-Forgeability Bad (2) Composition iron. 0.41% carbon. Balance titanium.Ultimate. tensile strength (p. s. i.) 155,000

Balance titanium. Ultimate tensile strength (p. s. 1).. 161,500

Proportional limit (p. s. i.) 120,000 Elongation (per cent in 2") 10.9Electrical resistivity (ohm-cm.) 139 10- Forgeability Good It is notedthat the tensile strength, proportional limit and elongation have thusbeen materially increased by the combination of aluminum and iron intitanium with the addition of the carbon thereto. As shown above, thetensile strength and elongation characteristics of titanium aluminum ortitanium iron alloys has been increased by forming a ternary alloy oftitanium, aluminum and iron. It may be seen, also, by referring to thetable below, that the tensile strength and elongation of such ternaryalloys formed by the combination of aluminum and iron with titaniumdepends upon the amount of aluminum and iron which is present in theternary alloy. After experimentation, it was found that thecharacteristics of tensile strength and elongation are dependent uponthe amount of aluminum and iron present, as follows:

Ultimate Percent Percent Tensile Aluminum I strength pc 2 (p. s. i.)

In addition. to the alloys thus formed by the combination, of aluminum,iron and titanium to form av ternary alloy, the alloy may be. modifiedby an. addition of up to 1% silicon to form a new quaternary alloy or alive element alloy consisting of titanium, aluminum, iron, silicon andcarbon.

The addition of silicon to any one of the. ternary alloys of aluminum,iron and titanium was found to generally improve the tensile strengthand proportional limit thereof. It wasalso found that silicon. does notaffect the hot workability of. these alloys.

A. preferred alloy, as shown below, had the following properties:

Composition:

3% aluminum. 1% iron. 0.5% silicon. Balance titanium. Ultimate tensilestrength (p. s. i.)' 161,800

Proportional limit (p. s. i.) 147,000 Elongation (per cent. in. 2") 10.9Modulus of elasticity (p. s. i.) 18 10fi Electrical resistivity(ohm-cm.) 1 18x10 The alloys are made in an inert atmosphere, typifiedby argon or helium, provided the alloy is melted or sintered. The alloyscan also be made in a vacuum environment. If the alloys are melted, thecrucible can be graphite or a highly refractory oxide, preferably thoria0r stabilized zirconia or carbides of. tungsten and boron. If thealloys-are arc-melted, in which case an inert atmosphere or vacuum muststill be used, the crucible can be water cooled copper. Powdermetallurgy methods can also be used. The tensile properties 01 thealloys, herein described, will vary according to the method used, butare better than the unalloyed titanium in every case.

The subject alloys are not modified appreciably by heat treatments.Quenching from l000 C. does, however, increase the strength andembrittle the alloys. The hardness of the alloys is not increased byquenching but does increase when heated at 500 C. for 4 hours afterquenching after 1 hour at 900 C. It was found that a heat treatment of 5hours at 700 (3., followed byfurnace cooling, did not afiect theultimate tensile strength of a 5% aluminum-5% iron-titanium alloy, butit did increase the proportional limit from 144,000 p. s. i. to 162,000p. s. i. and decreased the elongation from 7.0% to 6.2% in 2".

The forming of alloys containing aluminum and iron is done by forging tothe desired shape at a metal temperature not to exceed 1200 C. Thenormal forging temperature of 950 C. does 1 not cause excessiveoxidation.

An alloy containing approximately 2% aluminum and 2% iron was hot rolledat 800 C. The alloy was cold rolled to 37% reduction in area andannealed. The properties of this sheet 3, were:

Cold Hot Rcllcd Rolled and.

Annealed Ultimate Tensile Strength (p. s i) 161, 500 133, 000 Propcrtonal Limit (p. s. i.) 105,000 108. 000 Elongation (percent in 2) 10.214. 4

2. A titanium base alloy consisting of 0.75%

to 6% aluminum, 0.75% to 7% iron, 0.25% to 0.75% carbon, 0.25% to 1%silicon, the rest being essentially all titanium.

ROBERT H. DICKINSON. LEE S. BUSCH.

References; Cited in the file of. this patent UNITED STATES PATENTSNumber Name Date 2,575,962 Jaffiee et a1 Nov. 20, 1951 OTHER REFERENCESProduct Engineering, November 1949, page 148.

Journal of Metals, March 485-487, 492, 498, 504, 5 14 and 539.

Titanium? Report of- Symposium, December 16, 1948, sponsored by Ofiiceof Naval Research, pages 73-75 and 132-134.

1950, pages

1. TITANIUM ALLOYS CONSISTING OF FROM 0.75% TO 6% ALUMINUM, 0.75% TO 7%IRON, FROM 0.25% TO 1% SILICON, THE REST BEING ESSENTIALLY ALL TITANIUM.2. A TITANIUM BASE ALLOY CONSISTING OF 0.75% TO 6% ALUMINUM, 0.75% TO 7%IRON, 0.25% TO 0.75% CARBON, 0.25% TO 1% SILICON, THE REST BEINGESSENTIALLY ALL TITANIUM.